MUSICINNEILSHUBINVO/OCWhenIlookatmyfellowhumans,Iseeghostsofanimalspast.Glimpsesofanepicstorythat’shiddeninsideusall.Myname’sNeilShubin.Asascientist,Ilookathumanbodiesdifferentfrommostpeople.Thewaywegripwithourhands,wecanthankourprimateancestorsforthat.Howwehearsomanysounds,thatdatesbacktocreaturesthesizeofashrew.Andthefurtherbackwego,thestrangeritgets.Torevealwhywelookthewaywedo,we’lltravelthroughthedistantreachesofourfamilytreeandmeetanunusualcastofcharacters.Theancestorsthatshapedyourbody.Thefamilyyouneverknewyouhad.FromthebadlandsofEthiopia…She'sbeautiful.…totheshoresofNovaScotia…Thisisthespot.…we’llsearchforcluesthatlieburiedinrock.Hiseyesarelikeglobesandhe’slike,"Ifoundit,Ifoundit."…andsearchforanswerswritteninourDNA.PETERHOLLANDVOIthinkitgivesusaglimpseintothebrainofourancestors.NEILSHUBINOC/VOImean,Ifindthatmind-blowing.Theadventurebeginswithasearchforsomeofourmostelusiverelatives,fishthatcrawledontolandhundredsofmillionsofyearsago.Fromournecksandlungs,toourlimbsandhands,weowealottotheseintrepidpioneers.Soifyoureallywanttoseewhyyou’rebuiltthewayyouare,it’stimetomeetyourinnerfish.MUSICOUTMUSICINTEDDAESCHLERVOWow,lookatthat.Paradise.NEILSHUBINVOYeah.TEDDAESCHLERVOThatisperfect.NEILSHUBINOC/VOHe’sgoingrightupthevalley.TheCanadianArcticisoneofthemostdesolateregionsoftheplanet,butthere’snowhereelseI'dratherspendthesummer.NEILSHUBINVOWhatdrawsmehereistreasure–mykindoftreasure:fossilshiddeninsideancientrocks.Inparticular,thefossilsoflongdeadfish,butnotjustanyoldfish.I’mhuntingforfishthatcarrythestoryofourownbodiesinsideofthem.HowIgothereandwhatIfoundcouldchangethewayyouthinkaboutyourselfandyourbody.NEILSHUBINVOThisisastorythatendsontopoftheworldwiththemostimportantdiscoveryofmylife.ButitbeginsinthecityofChicago,witharoomfullofhumancadavers.NEILSHUBINVOItwasmorethanadecadeago,andI'djustmovedtotheUniversityofChicagoasChairmanoftheAnatomyDepartment.AndIremember,youknow,hangingaroundwiththestudentsaroundthetableshere,justgettingto

knowthemandlettingthemgettoknowme.They’relaunchingtheircareersasfuturephysiciansandthere’ssomenervesandskittishnessthosefirstfewdays…MUSICOUTNEILSHUBINVO/OC…andthey'dalmostinvariablyask“Dr.Shubin,whatkindofdoctorareyou?Youknow,areyouasurgeon?Areyouacardiologist?”AndI'dsay“Well,no,I'mafishpaleontologist.”AndI'dgetthislooklike“What?Iwantmymoneyback.”Butitsoonbecameclearthatbeingapaleontologist,andnotjustanypaleontologist,afishpaleontologist,isaverypowerfulwaytoteachhumananatomy.Becauseoftensomeofthebestroadmapstoourownbodiesareseeninothercreatures.MUSICINNEILSHUBINVONowyoumightnotthinkyourbodyhasmuchincommonwithafish,butIseeafamilyresemblance.Onthesurface,youarenotveryfish-like,I'lladmit.Butyouarerelatedtothem.Andthecluestothatconnectionareetchedinancientstone.NEILSHUBINVOFossilsunearthedaroundtheworldrevealthatfisharethefirstcreatureswithbonyskeletons.Theyhavebackbonesandskulls,justlikeyouandme.Thissharedanatomyconnectsustofishandtoalonglineofotheranimals.ToseewhatImean,imaginethecompletehistoryoflifeonagiantfamilytree,fromthefirstmicroscopicorganismsbillionsofyearsago,toallanimalsalivetoday.NEILSHUBINVOOurhistoryliesononebranchofthistreeoflife,andwecantraceourancestryback.Around400millionyearsago,you’llfindfishswimminginoceansandstreams.40millionyearslater,thefirstamphibiansappearonland.Thenweseereptiles,followedbythefirstmammalsaround200millionyearsago.Andmuchlater,wearriveatourspecialbranch:primates.Thishistorytellsussomethingremarkable.Everyreptile,birdandmammalalivetodayisdescendedfromancientfish,andthatincludesus.MUSICOUTMUSICINNEILSHUBINVO/OCSohowdoesthislegacyplayoutinouranatomy?Eachoneofus,walkingaroundinthislabtoday,carriesthehistoryoflifewithinus.Andtheevidenceisseenineverypartofourbodies.Andnotjustinourbones.Eventhecomplextangleofnervesinsidethehumanheadmakesmuchmoresensewhenyourealizeit’sthesamebasicwiringfoundinfish.Butthere’sonedefiningpieceofhumananatomythatseemsremotefromtheworldoffish.AndIvividlyrememberwhenitfirstcapturedmyimagination.WhenIwalkedintotheanatomylabforthefirsttime,IwassortofscaredaboutwhatIwasgoingtosee,whatIwasgoingtofeel.Buttherealityis,afterthefirstfewweeks,thatfearturnsintoasortofacockyself-confidence.MUSICOUT

NEILSHUBINVOAndthesethings,youknowwhenyoudissectthem,itdoesn’tlookveryhuman,itkindoflookslikeawaxmodelinalotofways,butthenyouhitthehand.MUSICINNEILSHUBINVO/OCAndforme,asIunwrappedthegauzeandrevealedthepalm,thefingers,thefingernails,somethingelsehitmeentirely.Andthatwasadeepsenseofconnection,aconnectiontoanotherhumanbodylyingonthatslab.ThiswasnotawaxmodelthatIwasdissecting,thisformerlywasapersonwholivedalifejustlikeIamlivingnow.WhenIseetheanatomywithinthehumanhand,I'minaweoftheintricateconnectionsbetweenbone,tendonandmuscle.Reallyit’sthroughtheactionofthesemusclesthroughthetendonsthatthehanddoesits,youknow,doesitsmagic,ifyouwill.Sothatwhenthemusclesfire,itpullsonthesetendonsandwatch,thefingersflex.MUSICOUTNEILSHUBINOC/VONow,thefinemusclesofourhand,theselittletinymusclesthatliealongthetendons?Thesearethemusclesthatcontrolthefinemotionofourfingers.Thesearetheonesthatarequintessentiallyprimateandhuman.MUSICINNEILSHUBINVOSowheredidthismarvelofevolutioncomefrom?Itclearlyhasdeeprootsinthepast.NEILSHUBINVOAndyoucanseeevidenceofthatinthebonesofmoderncreatures.Morethan150yearsago,scientistswerefindingconnectionsbetweenthehandsandlimbsoffourleggedanimals.MUSICOUTNEILSHUBINVO/OCSirRichardOwenwasananatomistinthe19thcentury;hewasfortunatetobeananatomistinanageofdiscovery.MUSICINNEILSHUBINVOAndsopeoplewerecomingbacktoLondonwithnewandoddballcreaturesforhimtoanalyze,andinanalyzingallthedifferentcreatureshefoundcommonpatterns.Althoughtheoverallshapeandstructureofeachlimbwasverydifferent,hestartedtoseethattherewasanunderlyingtheme.Itwasasifthesamesetofboneswasbeingsquashedorextendedtoperformdifferentfunctions.NEILSHUBINOC/VOHere’sadog.Dogs,youknow,runandjump,whatdoyouhave?Onebone,twobones,littlebonesandthenthedigits,theequivalentsofthefingersortoes.And,ofcourse,here’sabird.Itslimbhasbeenmodifiedintoawing,andithasonebone,twobones,lotsofbones,andthendigits.Theamazingfactis,ineachofthesecreatures,theskeletalarchitectureislargelythesameasours.Andwhatwasutterlysurprisingisthattheskeletonofeveryanimalwalkingtheearthtodayhasthisfundamentalpatternofonebone,twobones,littlebones,fingers.Owendidn’tknowwhycreatureshadthatpattern.Itwasamysterytohim.Itreallytookanewinsight,aninsightfromCharlesDarwin,

whichbasicallysaidthereasonwhyanimalshavethiscommonpatternisbecauseatsometime,inthedistantpast,theyallsharedacommonancestorthathadaversionofthispatterntoo.MUSICINNEILSHUBINVOAccordingtoDarwin,weshouldbeabletotracetheevolutionofourlimbsandhandsbygoingbackintimedownourfamilytree.Startingwithourprimateancestors,weseehandsandlimbsthatlookverysimilartoourown.Gobackabitfurthertothefirstmammalsandwefinddeepersimilaritiesinthepaws.Andweseehowpawsemergedfrommoredistantrelatives.Andifwegobackevenfurther,wereachourmostdistantfour-leggedancestors.Theseanimals,theearliesttetrapods,wereamongthefirsttohaveOwen’s“onebone,twobones,lotsofbones”pattern.Butwhenweentertheunderwaterworld,around400millionyearsago,insteadofanimalswithlimbs,wefindprehistoricfishwithfins.Andthatbringsustoagreatmysteryofbiology.Howdidwegetfromfishwithfinstoanimalswitharmsandlegs?Darwinboldlypredictedthattheremusthavebeenancientanimals,transitionalforms,thatbridgedthisgap.Butwhatwouldsuchananimallooklike?Wouldithavelimbs,orfins,orboth?Suchacreaturereflectsacriticalstepintheoriginofthehumanhand.Isetouttofindone.MUSICOUTNEILSHUBINVOIstartedmysearchbackintheearly‘90s,whenIworkedinPhiladelphia.NEILSHUBINVOOkay.Iknewthatfindingthistransitionalfishwasgoingtobeatallproposition.TEDDAESCHLEROC/VOAlotofthemaroundintheChicagolab.NEILSHUBINVOAndthefirstquestionwaswheretolook.Theworld’sabigplace.TheEarthisagiantplanet…NEILSHUBINOC…andfossilsareverysmall,sohowdoyoufindthosethings?MUSICINNEILSHUBINVOWellthere’sachecklistwerunthrough.Welookforplacesintheworldthathaverocksoftherightage.Ifyou’reinterestedintheoriginofdinosaurs,there’soneageofrocktolookat.Ifyou’reinterestedintheoriginoftransitionalcreaturesbetweenwaterandland,there’sanotherageofrock.NEILSHUBINVOThenyoulookforplacesintheworldthathaverocksoftherighttype.Thekindsofrocksthatarelikelytoholdfossils.WeknewfrompreviousdiscoveriesthatrocksfromtheDevonianera,around360millionyearsold,werelikelytocontainearlytetrapodfossils.AnditturnedoutwehadrocksofthatagerighthereinPennsylvania.TEDDAESCHLERVOTheotherthingisthat.

MUSICOUTNEILSHUBINVOTolookforgoodsitesIteamedupwithgeologist,TedDaeschler,andwe’vebeenfossil-huntingbuddieseversince.TEDDAESCHLEROC/VOYouknowwhat?We'vetrieditthroughhere,evengoingdownintoWestVirginia.Wearesortofmaybeanoddcouple.TEDDAESCHLEROCNeilisexcitableandenthusiastic,whichiswonderful.I’menthusiasticaswellbutIthinkmaybenotquiteasvociferous.TEDDAESCHLERVOImighttendtohunkerdownmoreandfocusonrecoveringthematerialaswestarttofindit.AndNeilmightbealittlebitmore,"Okay,what’soverthenexthorizon.What'soverthenexthill?"TEDDAESCHLEROCNeilisonthatedge,alwaysthinkingaboutthenewplacetogo.MUSICINNEILSHUBINVOTedandIwouldsitinthecarwithmapsinonehand,andgeologicalpapersintheother,andwetootledthroughthesestateroads,lookingattherocks,saying,"Okay,whatkindofrockisthisagain?Whatkindofageisit?"ButtheprobleminPennsylvaniaisthatit’snotadesert.Thebedrockisnotexposedtothesurface.Youhaveforests.Youhavegrass.TurnsoutthebestexposuresofrockinthestateweremadeforusbythePennsylvaniaDepartmentofTransportation,becausetheywoulddynamite.They’dexposedsectionsofthegeologicalrecord.NEILSHUBINOCAndweeventuallyhitthisoneroadcut…NEILSHUBINVO…agiantexposure.It’scalledRedHill.TEDDAESCHLERVOItprobablyis.NEILSHUBINVOOh,myGod.Andthenweknew…NEILSHUBINOC…okay,thiswastheplacetohit.MUSICOUTNEILSHUBINVOWehadambitionstoexploretheglobe.Butourfirstexpeditiondidn’ttakeustoanexoticdeserthalfwayaroundtheworld…

MUSICINNEILSHUBINVO…ithappenedbythesideofaPennsylvaniahighway.TedrevisitedRedHillonetimewhenIwasnotthere.MUSICOUTNEILSHUBINVOHemadeaphonecalltome.Hesays,"Hey,Neil.IthinkI'vefoundsomethingreallyimportant."Isaid,"Well…NEILSHUBINOC…whatdidyoufind?"He'slike,"IthinkIfoundatetrapod."Isaid,"Ted,youkiddingme?Imean,no.You’renotgoingtofindatetrapodonyoursecondorthirdtriptoRedHill.Thisgonnatakeyearsofwork."TEDDAESCHLERVO/OCSo,Iwasmovingalongthislayerandsawbeautifullittlefossilbonematerial,chippedarounditalittlebit,right,rightonthislayer,andloandbehold,uncoveredwhatturnedouttobeaverysignificantspecimen.MUSICINTEDDAESCHLERVO/OCThisistheshouldergirdleofanearly,limbedanimal.Itwasanewspecies.Itwasawholenewkindofanimal.Andalthoughweonlyhaveashouldergirdle,it’sactuallyaveryinformativepartoftheskeleton.Itwouldbeontheleftside,theskullwouldgooffinthatdirection,andtheanimalitselfwouldbeaboutameterlong.Andjustfromtheshouldergirdlewecanlearnthingsabouthowitmayhave…TEDDAESCHLERVO…heldthatlimb.Andofcourse,itdoescomparetootheranimalsthataresimilarfromotherpartsoftheworldandwecanusethosetolearnotheraspectsofHynerpeton.NEILSHUBINVOTheseearlyfour-leggedanimalsbelongtoagroupIliketocall‘TheStegas.’MUSICOUTMUSICINNEILSHUBINVOSomeofthebestspecimenshadbeenfoundinGreenlandbyapaleontologistnamedJennyClack,whobeganworkingthereinthe80's.JENNYA.CLACKVOTheideaoftransitionbetweenanimalswithfinsandanimalswithlimbs…JENNYA.CLACKOC…hasbeenthoughtaboutforalongtime.Butuntilrecentlytherehadonlybeenthreedatapoints.Somethingwasobviouslyafishatoneend;somethingthatwasobviouslyananimalwithlegsandwalkingaroundattheotherend,andinthemiddle,wasthisverypeculiarthingcalledIchthyostega.

NEILSHUBINVOUsingthelatestscanningtechniquestobuilda3DmodelofIchthyostega,Jenny’stryinggetabettersenseofhowthiscreaturelived.She’sworkingwithanimalmotionexpertStephaniePierceatLondon'sRoyalVeterinaryCollege.MUSICOUTSTEPHANIEPIERCEVO/OCBasicallywhatwewantedtoseewashowmuchmovementwaspossibleateachofthelimbjoints.Andhowthiscomparedtomodernanimals.NEILSHUBINVOTheycomparedIchthyostegatomoderntetrapods…MUSICINNEILSHUBINVO…likesalamanders,tofigureouthowthisfossilmighthavemoved.Usingpressurepadsandhigh-speedcameras,theycouldmeasurehowthelimbsofmodernanimalsworkandcomparethistothebonesofIchthyostega.JENNYCLACKVOIchthyostega’sforelimbscouldpush…MUSICOUTJENNYCLACKVO…thetophalfofthebodyofftheground.Butthebackendhasgotthesepaddle-likehindlimbs,whichareusefulinwaterforswimmingwith,butonlandactasstabilizerstostopthethingtopplingover.MUSICINNEILSHUBINVOAnatomyofthebonessuggestedthatthisfour-leggedanimalhadjustcomeontoland.Itwasrightattheedgeofoursearch.Butbetweenthesetetrapodsandancientfish,therewasstillagapspanningmillionsofyears.Ifwecouldfindananimalwithinthatgap,we’dbefillinginacrucialpieceofevolutionaryhistory.MUSICOUTTEDDAESCHLEROCThereitis.NEILSHUBINOC/VOYeah.Sonowtherewasanewchallenge,whereonearthshouldwelooknext?Iremembersittingintheoffice…NEILSHUBINOC…andweweredoingthesortofusualbanteronedayaboutsomethinggeological.MUSICINNEILSHUBINVO

Wehadacollegetextbookandwerejustthumbingthoughthediagramsinthebookandboomtherewasthisfigurethatchangedourlives.TEDDAESCHLERVOThere'sthemap.NEILSHUBINVOItwasamapofNorthAmerica,whichhighlightedthreeareasofDevonianrockofjusttherighttypetoholdfossilfishmovingontoland.TherewereourRedHillrocksinPennsylvania…TEDDAESCHLERVOBeentheredonethat.Workedonthoseveryrocks.NEILSHUBINVOThentherewererocksinGreenland,whichJennyClackhadalreadysearched.TEDDAESCHLERVO/OCBut,itwasthatlittle.NEILSHUBINVOFinally,therewasthisstripacrossnorthernCanadaandtheserocksweretenmillionyearsolder.MUSICOUTNEILSHUBINOC/VOIrememberseeingthatandsayingtomyself,"Holycow.Thisiswhatwe’relookingfor."MyheartwasracingwhenIsawthatbecauseno…TEDDAESCHLEROCYeah.NEILSHUBINOC/VO…paleontologisthadworkedonthatexpresslylookingforearlytetrapods.Thenyoudugouttheaerialphotos,andthat’swhenIgotkindofterrified.Irememberseeingthis…TEDDAESCHLERVOIknow.NEILSHUBINVO/OC…forthefirsttime,thinking,"Yougottobekiddingme.Youknow,lookatallthissnow.Howdoyouworkthere?"MUSICINNEILSHUBINVOAllright,soone,two,three,four,five,six,seven,eight.MALEDISPATCHERVOOkay,two-sixisclear.NEILSHUBINVO/OC

Backin1999,whenweembarkedonourfirstArcticadventure,wehadlittleideawhatwewereinfor,northatwewerestartingasearchthatwouldlastoveradecade.Wow,thatisalotofsnow.HereintheHighArcticofCanada,therearenohumansettlementsformilesandmiles.Noroadsandallyou’vegotiswhatyoubringwithyou.Herethere’salwaystheriskofbeingtrappedbysomeoftheworstweatherontheplanet.We’reenteringthevalleynow.TEDDAESCHLERVOThisisthebiggate.NEILSHUBINOCOh,theresheis.TEDDAESCHLERVOYep.NEILSHUBINVOI’mlookingrightatthequarry.WehadanarrowwindowduringthemonthofJuly,whenthesnowmeltsjustlongenoughtoletusin.MUSICOUTNEILSHUBINVO/OCWeweretrainedfossilhunters,butnowwewouldhavetofigureouthowtobecomeArcticexplorers.SowhenthehelicopterdropsyouoffintheArcticforthefirsttime,you’restandingheresaying,"WhatamIdoinghere?"Youknow,you’rethinking,"Oh,polarbears",that’sthefirstthingyoulookfor.Isthereanythingonthelandscape?Everythingwhitebecomesapolarbear.Thelastthingonyourmindarefossils.MUSICINNEILSHUBINVO/OCIt’shardtobelievewhenyoulookoutacrossthisfrozenterrainthatoncethiswasawarm,wateryworldswimmingwithlife.HereweareintheArcticandwehaveasnowstormcomingand,youknow,we’relookingatrocksbehindus,butthere'sthishugedisconnectbetweenthepresentandthepast.Whatweseetodayisvalleywithredandgreenrocks,thataretilted,stackedoneontopoftheother,butthat’snothowitwasinthepast.Thesevalleyshavebeencarvedbyglaciersthathavemovedbackandforth.Andthoseredandgreenrocksactually,atonepoint,extendedacrossthevalleyandtheywerestraight.Theyweren’ttilted.Nowlookinsidetherocksandwhatthoserockstellusthatthisvalley,375millionyearsago,wasagiantfloodplainandthatfloodplainwasfilledwithriversthatswelledtheirbanksandsometimesshrunk,butinthoseconditionsformedswampsandstreamsofalldifferentsizes.NEILSHUBINVOAndinsidethosestreamswasdiverselife.NEILSHUBINVOSomewhereoutthere,wewerehopingtofindanintrepidfishonthebrinkofthehistorictransitiontolifeonland.MUSICOUTNEILSHUBINVOCouldweeverfindevidenceofthismomentouseventburiedinsediments…MUSICIN

NEILSHUBINVO…thathadbeencrushedanddistortedby375millionyearsofgeologicalupheaval?Whenyouthinkabouteverythingthathastogorightforacreaturetobefirsttobeafossilandthenacreature’sfossiltobediscoveredbyapaleontologist.Itislikefindinganeedleinahaystack.Weweredeterminedtofindthatneedle.Ifitwasoutthere.MUSICOUTMUSICINNEILSHUBINVOBackinChicago,Ihadanotherwayoftracingtheanatomy…NEILSHUBINVO…wesharewithfish,usingadifferentkindofwindowintoourevolutionaryhistory.WhenIwasn’tlookingforfossilsinthesummers,I’dspendmytimelookingunderamicroscopeatembryos.AndIwaswatching,atthetime,bodiesformingfromeggtoadult.Andthereisanincrediblebeautytothatprocess.NEILSHUBINVO/OCIntheearlystagesofdevelopmentallanimalsstartasasinglecell.Theydivideagainandagainuntilgraduallyabodyemergeswithafront,aback,atopandabottom.Itbecameveryclearearlyonintheprocesssomeofthemostimportantembryoswerefish.Becausefishhavethebasicbodyplanintheirembryosthatwastobecomeourownbodies.NEILSHUBINVOIfyouseeanearlyfishembryoandahumanembryosidebyside,you’llseesomethingremarkable.Theylookalmostidentical.Wereallydolooklikefish.Bothembryoshaveahead,abody,atailandmanyothersimilarfeatures.NEILSHUBINOCAndoneofthosesimilaritiesexistsintheneckorwhat’scalledthepharyngealarea.NEILSHUBINVOInbothfishandpeople,whatyoufindareaseriesofswellingscalledgillarches.Turnsoutthatinfish,thoseswellingsbecomecomponentsofthegillapparatus.Inpeople,theybecomeportionsofourlowerjaw,portionsinourmiddleearandpartofourvoicebox.Sothis…NEILSHUBINOC…isawonderfullyelegantdevelopmentalprocess.MUSICOUTNEILSHUBINOCButsometimesthingsgowrong.MUSICINNEILSHUBINVO/OCAndwhentheydo,yourinnerfishcancomeout.SomykidsarereallygoodfriendswiththeRichardsons,onedayIgetane-mailfromSeth,theirfather,whosays,"Doctor,mywife’safish."AndIsaidtomyself,"Igottocheckthisoneout."We’rehereforthefish.

SETHRICHARDSONOC/VOThefishisavailable.It’sfresh.Comerightthrough.Ithinkifyougotowardstheback.NEILSHUBINOCOh,we’llcutthrough,yeah.HeySeth,isthisyourfamilyalbum?SETHRICHARDSONVOYes,exactly.NEILSHUBINOC/VOSoyou’reafish?Nowfirstoff,ifyouare,andyou’remoreofafishthanIam…MUSICOUTMOLLYRICHARDSONOCYes.NEILSHUBINVO…I'mveryjealous.Soproveit.MOLLYRICHARDSONVOAllright.Well,hereitis.There’smygill.NEILSHUBINVO/OCRightthere.Sowhathappensduringdevelopmentisweallhavegillarches.Wealldevelopthem.Thislittlepitisaleftoverfromanancientgill.AndIamincrediblyjealousofyou,Molly,becauseyouaremoreofafishthanIam.We’reallfish,butsomearemorefishthanothers.MOLLYRICHARDSONVO/OCThat’sright.Somejusthaven’tevolvedveryfar.NEILSHUBINVO/OCNo,you’retheluckyone.Sowhat’sreallycooliswhenyouknowpaleontologyanddevelopmentalbiology,manyofthemusclesandnervesandbonesI'musingtotalktoyouwithrightnow,andmanyofthemusclesandnervesandbonesyou’reusingtohearmewithrightnow,correspondtogillstructuresinfish.Youknow,andweseethatinfossils,weseethatinembryos,weseethatinDNA,Imean,andweseethatinyou.MOLLYRICHARDSONOCMybrother-in-lawhaswebbedfeet.MUSICINNEILSHUBINVO/OCIloveyourfamilybytheway.Whilefeatureslikefishgillshavebeenretooledinouranatomy…NEILSHUBINVO/OC…otherbodypartsperformthesamejob,butendupindifferentplaces.Liketesticles.Well,we’reheretoseesomegonads.

DIRKOCOkay.NEILSHUBINOCFishgonads.MUSICOUTDIRKOC/VOOh.I’lljustdissectthislittleguyhere.NEILSHUBINVO/OCYeah,ifyoucouldpopthatbadboy,thatwouldbe.DIRKOC/VOSure.Comerightoutofthere.NEILSHUBINVORight.DIRKOCRightthere.NEILSHUBINOCYeah,youknow,sothereyousee,youknow,there’stheheart.DIRKOCRight.NEILSHUBINVOThere’stheliver,youknow.Thegonadisrightthere.DIRKVOLookatit.NEILSHUBINVOSoyouknowwhat’sfunkyaboutthesethings?Isthegonadistowardsthechest,rightneartheheart.Youknow,butwhat’sstunningisyouandI,likeeveryothermammal,youknow,ourgonadsstartedupthereanddescendeddowntohere.DIRKOCItmightbebetterwheretheywere.No.It'ssaferthatway.NEILSHUBINOCWell,insomesenses,theywould.MUSICINNEILSHUBINVO

Havinggonadsclosetotheheartisfineforourcold-bloodedfishyrelatives,notsogoodforwarm-bloodedmammals.Spermcan’tstandtheheat,sothat’swhyourtesticleshavetodroptoacoolerplace,outsidethebody.Whenahumanembryodevelops,thegonadsstartdeepinthebody,justliketheydoinfish,andthendescendthroughthebodywall,mirroringevolution.Butthatcreatesaweakspotinmaleswhereourgutscanpopthrough.Thisleavesusvulnerabletocertainkindsofhernias.Youknow,youthinkaboutwhyhumanshavehernias…MUSICOUTDIRKOCOkay.NEILSHUBINOC…it'sbecauseourtestesdescend…DIRKOCRight.NEILSHUBINOCAndtheystartuphere,theygodownintothescrotumandthebodywallgetsweakerbecauseofthatreconfiguration.DIRKOCThatpassingofthetesticles.Okay.NEILSHUBINOCYeah.Andso,youknow,we’llfind,youknow,we'llfindthatyouhaveaweaknessinthebodywallinsomecasesandfolksgethernias.DIRKOCAndthat’swhyfishdon’tgethernias?NEILSHUBINOCThat’swhyfishdon’tgethernias.MUSICINNEILSHUBINVOFlawsinthehumanbody,likeoursusceptibilitytohernias,remindusthatwe’realladaptedfromancientancestors.Weare,everyoneofus,justajerry-riggedfish.MUSICOUTNEILSHUBINVOInJuly2000…MUSICINNEILSHUBINVO/OC…wewerebackintheArcticforasecondseason,continuingthesearchforourelusivefossil.Now,we’veactuallyfoundfloatboneonthislevel,solet’sjuststayclose.Wewidenedourexplorationsacrosstheregion,butwewere

findinghardlyanything,letalonethetransitionalfossilofourdreams.Then,justbeforewebegantopullout,weweresuddenlyconfrontedwiththerealdangersofworkinginthiswilderness.Theteamhadseparatedintoseveraldifferentgroups,weusuallygooutinpairs,becauseit’s,youknow,adangerousplace.Onepairwentdownthevalley,another…NEILSHUBINOC…wentupthevalley,youknow,wespreadapartfortheday.NEILSHUBINVO/OCTwo-six,two-sixthisisBirdFjord.ThisisBirdFjord,over.Weallreturnedtocampattheendofthedayandtheideaiseverybodyneedstoreturnbacktocampbyradiocall.It’sseveno’clockwhenwemakeoursafetycheckbacktothestation.Andsowe’remakingdinnerandwe’rewaitingfortheradiocall,andyouknowkindoflooking…NEILSHUBINOC…around,it’slike,"Hey,youguysseenJason?""No,Iain’tseenJason.YouseenJason?"Isaid,"Iaskedyouthatquestion.Youdidn’tseeJason?"AndallofasuddenitbecamenobodysawJason.Where’sJason?NEILSHUBINVOThisisouryoungestmember,wewerelookingoutforhimtheentireseason,andnoJason.NEILSHUBINOCImean,myheartwasreallybeginningtorace.ThenIhearfootstepsoutsidethetent,thetentflyopens,andthere’sJason.Hiseyesarelikeglobes,andhe’slike,"Ifoundit.Ifoundit."AndIwaslike,"Jason,whatdidyoufind?Didyoufindapolarbear?What?"NEILSHUBINVOImeaneverypocketwasburgeoningwithbones.Hegoes,"Igotthese…NEILSHUBINOC…bones."He’slayingthemoutonthetable,oneafteranother.NEILSHUBINVOIt’sdaylight24hoursaday.SowerandowntoJason'ssiteandbeganthatnight,tocrawlit,lookingforthelayerthatwaskickingoutthebones.Assoon…NEILSHUBINOC…aswecametothisbluffhereandlookeddown…MUSICOUTNEILSHUBINOC…wesawwhyJasonwassoexcited,becausebeneathourfeetwerefossilfishbones,fragmentsoffossilfish,manyofthem,thousandsofthem.Itwasn’tjustonefish,itwasawholeaquarium.Itwasdifferentspecies.Itgotbetter,becauseaswewalkedupthehillandwefollowedthatcarpetoffossilfragments,itstopped.Meaningitlikelycamefromonelayer.Andifwehadanyluckatallwe’dfindthatlayerandseewhat’sinside.NEILSHUBINVO/OCThat'snot.Butthereisthisherethough.Ittookseveralweeks,butweeventuallylocatedthelayerofrockfromwhichthefossilfragmentswerespilling,andthenlookedfortelltalesignsofbonesprotrudinginthehopeitmightleadustomorecompletespecimens.Youcanseethistiniestlittlewhitefleckhere…thattoldusstop,youknow,

becausethatlittlewhitefleckshowsthestructureofascale.Andthenyoulookcarefullyandit’sclearlyascaleonend.Andonceyouseethatscaleonend…MUSICINNEILSHUBINVO/OC…youseeanotherpieceofbonehere.Youseeanotherpieceofbonehere.We’reonthelayeritselfsoit’samatterofstop.Nowwhatwe’regoingtodoisremovethisiceandrubbletoexposethelayerasalittleplatform.Onlyaperson.Toreachtheburiedfossils,we’dneedtominetherockface,butwewererunningoutoftime.Allright,let’sgetthatrockoutofthere.Onceagain,ourshortwindowofsnow-freeweatherended.MALEDISPATCHERVONow,areyouguyslookingforthatflighttomorrow?Orwereyouguysdelayingituntilthefourth?NEILSHUBINVOWe’reaboutthreeaway.MALEDISPATCHERVOOkay.Rogerthat.NEILSHUBINVOWe’dhavetowaitanothersummertodigoutourancientriverbed.MUSICOUTMUSICINNEILSHUBINVOBackhome,averydifferentkindofscientificadventurewasunfolding.Arevolutionwasunderway…NEILSHUBINVO…inevolutionarybiology.Onethatwouldrevealaprofoundgeneticconnectionbetweenfinsandlimbs.Mylabwouldplayaroleinthesearch,butwewerepartofamuchbiggereffort.MUSICOUTNEILSHUBINVOAttheforefrontofthisquestwasmycolleague,CliffTabin,ageneticistatHarvardUniversity.MUSICINNEILSHUBINVOCliffhadbeenfocusingonhowdigits,likefingers,form.Andinhiswork,hereliedonchickembryos.Forbiologists,chickeneggsofferawindowintotheprocessofdevelopment.CLIFFTABINOCIfyoutakeachickeggandcutaholeintheshellandthrowitaway…CLIFFTABINVO

…youcanseetheembryofloatingontopoftheyolk.It'srightthere.It'saccessible.Youcanstarttoprobewhat’simportantforittoformbyremovinglittlebitsandsaying,"Doesthatdisrupttheprocess?”Orbymovingtissuefromoneplacetoanotherandsay,"Whatdoesthatdo?”NEILSHUBINVOCliffwasfollowingalonglineofscientistsusingchickenstoinvestigatehowlimbsdevelop.NEILSHUBINVOInthe1950s,JohnSaunderswasonesuchscientist.Saundersandhisteamexperimentedonchickembryosjustafewdaysold.Theyfocusedonlittleprotrusions,calledlimbbuds,fromwhichthewingswouldeventuallyemerge.Inoneexperiment,Saunderstookasmallpatchofcellsfromonesideofabudandtransplantedittotheoppositesidetoseewhatwouldhappen.Whenhecamebackaweeklater,muchtohissurprise,hefoundthatthechickembryohadgrownasecondsetofdigits,oneamirrorimageoftheother.Thattinypatchofcellswasclearlyspecial.Somehowitwastellingthedigitswheretoform.CLIFFTABINVOThewaythatwenowthinkofitisthatthosecells…CLIFFTABINOC…instructtherestofthelimbbymakingalong-rangesignal,abeaconthattheysendoutthattheothercellsseeandrespondto.NEILSHUBINVOTheidentityofthatsignalwasagreatmysterythatwentunsolvedfordecades.NEILSHUBINVOButCliffhadahunch.He,andsomecolleagues,suspectedthatthesignalmightbeasinglemoleculethatcamefromasinglegene.NEILSHUBINVO/OCHebasedhissuspicionsonresearchthatwaschanginghowweunderstandtheroleofgenesinmakingbodyparts.Itwasworkthathadbeendoneonanentirelydifferentanimal.Itwasatinylittlecreaturethat’sreallysmall,thatbreedsveryrapidlyandthatyoucanstudyinthelaboratory.Andit’sthis.Thehumblelittlefruitfly.Bystudyinghowfruitfliesdevelop,scientistshadmadesomeamazingdiscoveries.Individualgenescandocomplexthings,likeguidingtheformationofentirebodyparts.Therewasonegene,dubbed“hedgehog,”thatcaughtCliff’sattention.Itstoodoutbecauseitseemedtosendoutanorganizingsignal.CLIFFTABINVOInafly,thissignal,hedgehog…CLIFFTABINOC…tolddifferentcellstodothingsinaparticularorderdependingonhowclosetheyweretothesourceofthesignal.NEILSHUBINVOCliffwonderedifagenelikehedgehogmightplayasimilarroleinchickens.Sohisteamtooktheflyhedgehoggene,andlookedforamatchinthechicken.Aftermonthsofsearching,theyfoundit.Then,remarkably,theydiscoveredthegenewasactiveinexactlythesamepatchofcellsidentifiedbySaunders.Theydubbedthisnewgene“SonicHedgehog,”afterthevideogamecharacter.SodidSonicHedgehogproducethemysterioussignaleveryonewantedtofind?

CLIFFTABINOCUltimatelywewantedtoknowwhetherthisgenethatwediscovered,SonicHedgehog,reallyisthekeysignalformakingthearrayofdigitsinthehand.NEILSHUBINVOInaground-breakingexperiment,CliffandhisteamaddedabeadcontainingpureSonicHedgehogtothewrongsideofthegrowinglimbbud,echoingSaunders’experiments.Whenhereturnedaweeklater,hefoundhischickhadtwosetsofdigitsjustlikeSaunders’chick.Thiswasamajordiscovery.SonicHedgehog,asinglegene,wasthesourceofthesignalresponsibleforgeneratingthepatternofthedigits.CLIFFTABINVOAndthatreallynailsit.MUSICOUTCLIFFTABINOCItreallymeantthatwehadthelinchpininourhandsandcouldstartlookingathowthatprocessworkedindetail.NEILSHUBINVOItturnsoutSonicHedgehogshapesnotjustthewingsofchickens,butthepawsofmiceandotheranimals,andevenourownhands.MUSICINNEILSHUBINVOIfyouwanttoseejusthowimportantSonicHedgehogistous,meettheHubbardfamily.MUSICOUTNEILSHUBINOC/VOCanIcountyourfingers?Letmesee.Icancount.Iwenttoschool,too.KAMANIHUBBARDVOOne…NEILSHUBINVOTwo…KAMANIHUBBARDVO…two…NEILSHUBINVO…three…KAMANIHUBBARDVO…three,four…NEILSHUBINVO…four,five…

KAMANIHUBBARDVO…six.NEILSHUBINVO…andsixisspecial.MRS.HUBBARDVOYay.NEILSHUBINOC/VOLookatthathand.Kamaniwasbornwithanextradigitoneachhandandfoot.Grabmy,squeezemyfingerashardasyoucan,letmeseeyourgrip.Noharderthanthat.Youcangowayharder.Oh.Oh!Whythishappenshadlongbeenamystery.ItturnsoutthatpeoplelikeKamanioftenhavemutationsthataltertheeffectoftheirSonicHedgehoggene.MR.HUBBARDOC/VOWiththeconditioninKamani,Ijustwanttoknowwhat’sallowinghimtobesodifferent?NEILSHUBINOC/VOThewayourarmsandlegsoriginallydevelopinthewombistheypushoutfromthebodyasalittlebud.Sowehavefourlittlebudsstickingoutofusaswe’relittleembryos.Thenthosebudsgrowout…MUSICINNEILSHUBINOC/VO…andeventuallytheygrowoutandtheyelongate.Whatyouhaveisapaddle,abigbroadpaddle.NEILSHUBINVOJustasinthechickenlimb,SonicHedgehogsendsoutasignaltoshapethepatternofourdigits.Whenit’sstrong,apinkyforms.Andasitweakens,onebyone,differentfingersaremadeuntilweendupwithfive.IfweturndownSonicHedgehog,fewerfingersaremade.ButifweweretoincreasetheeffectofSonicHedgehogwewouldgetextrafingers,likeKamani’s.CLIFFTABINVOItisreallyquitebeautiful…CLIFFTABINOC…thatsomethingassimpleasasinglesignalmovingthroughthelimbcouldhavesuchprofoundanddifferentialeffectondigits.NEILSHUBINVOWenowknewthatSonicHedgehogplayedapowerfulroleinshapingthelimbsofallsortsoffour-leggedanimals.NEILSHUBINVOSohowfarbackdiditgo?Coulditbealegacypasseddownfromtheearliestfish?MUSICOUTNEILSHUBINVO

Backinmylab,thatwasaquestionmypost-doc,RandyDahn,wastackling.MUSICINNEILSHUBINVORandywasinvestigatinganancienttypeoffish,skates,whoseembryosgrowinasaccalleda“mermaid’spurse.”RANDYDAHNVOIguessthethingthatstruckmethemostwhenIfirstopenedtheskateeggwashowshockinglysimilar…MUSICOUTRANDYDAHNVO…thatembryolookstoachickenembryo,amouseembryo,ahumanembryo.RANDYDAHNOCAsanembryologist,Ishouldhaveunderstood,ofcoursethey’regoingtolooksimilar,butstillwhenyouseethatyou’rethinking…RANDYDAHNVO…there’s400millionyearsofevolutionthatseparatesmefromthatembryoandat…RANDYDAHNOC…onestageinmylife…MUSICINRANDYDAHNOC…thatwasexactlywhatIlookedlike.NEILSHUBINVOIt’sclearwehaveasharedgenetichistorywithfish,butdothegenesthatshapeourhandsalsoshapetheseskatefins?Tofindout,RandymanipulatedtheskateembryoslikeCliffhaddonewiththechickembryos.HeputabeadcontainingtheSonicHedgehogmoleculeontheoppositesideofagrowingfinbud.RANDYDAHNVOAnditturnsoutthat…RANDYDAHNOC…SonicHedgehogwassufficienttocauseamirrorimageduplication,asecondfin,toformintheskate.NEILSHUBINVOThisisexactlywhatSonicHedgehoghaddoneinCliff’schickens.RANDYDAHNVOWewereabsolutelystunned.Andyouhavetorememberthatthisisaskateembryoandwhatthattellsusisthat…RANDYDAHNOC…theseverybasicpatterningmechanismsareperformingtheexactsamefunctions…

MUSICOUTRANDYDAHNOC…intheskate,intheshark,inthechicken,inthemouse,allthewayuptohumans.MUSICINNEILSHUBINVOWehadtracedSonicHedgehogallthewaybacktolifeinancientoceans.Agenethatdeterminestheshapeofourhandswasalsoshapingthefinsofsomeofourmostdistantfishrelatives.Ourinnerfishrunsdeep.MUSICOUTNEILSHUBINVOButtherewasstillabigmysterytosolve.MUSICINNEILSHUBINVO/OCHowdidourfishancestorsmakethetransitionontoland?Andwhatdidtheylooklike?Wewerestilllookingforourelusivefossil,frozenforeveronthebrinkofthisgreattransition.Eachsummer,wereturnedtoJason'sancientriverbedtocontinueexcavating.Weneededtomovelotsofrock,toexposethenarrowseamcontainingthefossils.Butthen,we’dswitchtobrushesanddentalpickstouncoverthedelicatefossilizedbone.It’sjustthisincrediblyfunnyparadox.Youknow,we’reinthishugelandscapeandwe’realwayscrampedtogether.Youknow,our,myhead’snexttoTed'sfeet.Mark'shead’snexttomyfeet.It’sthistinylittlespot.Itwasinsuchatinycornerofthisvastlandscapethatwefinallystruckgold.NEILSHUBINVOWell,itwasthesecondweekofJuly,in2004,wewereallworkinginseriesinthishole.AndStevesays“Hey,guys,what’sthis?”TedandIgorunningover…NEILSHUBINOC/VO…andwhatwesaw,wasthis"V"here,itwascoveredwithrock.Andassoonaswesawthis“V”andwesawtheseteethunderit,itbecameveryclearthatthislittle"V"we’reseeingisthetipofasnoutandthatthiswasasnoutofaflat-headedfish.Westoppedinourtracks.Aflatheadwasalikelysignofatransitionalfish.Herewasthesnoutofexactlythecreaturewewerelookingforanditwasstickingoutoftherocks.Soifwehadanyluckwhatsoever,therestofthecreaturewouldbe,youknow,encasedintherock.Sowedugallthewayaroundthefossil,leavingachunkofrockthatwethenencasedinplaster.Wecouldn’twaittoseewhatwasinside.Okay,wegethome.MUSICOUTNEILSHUBINOCWeknewwehadaflat-headedfish,buthowmuchofitdidwehave?Well,thenthepreparatorshadtotakeover.Theyremovedtheplasterjackets…MUSICINNEILSHUBINOC/VO…andthefirstthingtheydidwastoetchawayattherock,exposingthefrontpartofthesnout.Thenaboutamonthandahalfgoesby,andtheystarttofindtheorbits,theeyeholes,andthenweseetheshoulder,andthenweseethe

fins,andthenweseemoreandmoreandmoreandmoreuntilweseeprettymuchtheentiretopsideofthebody.What’sreallywonderfulaboutthisspecimenisthatwehavetheheadconnectedtoabody,andthebodyisconnectedtothefins,soweknowthatthisfincomesfromthisanimal,andweknowitssizeandhowitfitstogether.NEILSHUBINVOLater,wefoundpartsofotherspecimens.Andsomeofthesewerereallybig,uptoninefeetlong.ThelocalInuitpeoplenamedourfossil“Tiktaalik,”whichmeans“largefreshwaterfish.”Andaswetookstockofourdiscovery,therealexcitementbegan.HerewasananimalDarwinhadpredicted,arealanatomicalmixture.Ithadsomefeaturesoffish,likescalesandfinsandgills.Italsohadlungsforbreathingair.And,toourastonishment,ithadaneck,theearliestonelikeourseverfound.Butinsidethefinslietheclincher.WeseeanearlyversionofOwen’sonebone,twobones,lotsofbonespatternthatweseeinourownlimbstoday.Itevenhadakindofwrist,thefirstsignsofalinktothehumanhand.EverytimeyouflexyourwristorshakeyourheadyoucanthankTiktaalikanditsDevoniancousinsadaptingtolifeintheseancientstreams.NEILSHUBINVOUnlikeotherfish,Tiktaalikcoulduseitsnecktowatchoutforpredatorsandtohuntsmallerprey.Andbecausethosefinswerestrongenoughtoliftitsbodyoutofthewater,awholenewfrontieropened.Overmillionsofyears,thetwopairsoffinsinfish-likeTiktaalikwouldleadtothetwopairsoflimbsineverybonyanimalonearth.It’sapowerfullegacywecanseeinourownarmsandlegstoday.MUSICOUTNEILSHUBINOC/VOWell,tothinkaboutTiktaalik,thinkaboutthis,thinkaboutapush-up.Whatarewedoingwhenwedoapush-up?We’reusingthemusclesthatattachtoourchest,andattachtotheundersideofourarmtogiveusthepowertoraiseup;weuseourelbows,anduseflexionatthewrist,whichisveryimportantbecauseitallowsourpalmtocontacttheground.Here’sthefinofTiktaalik.Andwhatdoesithave?Ithasamassivesurfaceforaconnectionofmusclesthatwouldattachtheshouldertotheundersideoftheupperarm.Ithasevidenceofahighlymobileelbow,anditevenhasawristthatcanflexsothattheequivalentofthepalmcancontacttheground.Here’safishthatcandoapush-up.MUSICINNEILSHUBINOCIrememberlookingatthewristofTiktaalikforthefirsttime,andatthatmomentIfeltakintowhatIfeltintheanatomylab…NEILSHUBINVO…whenIsawthecadaveranditshand.Thehandactuallydefinesusinmanyways.NEILSHUBINVOWhenyouthinkaboutwhatmakesourspeciesuniqueandspecial,it’shavingthoughtsandbeingabletomakethosethoughtsreal.Andthewayourthoughtsbecomerealisthroughuseofourhands–tobuildthings,tomakethings.Yetthebasicformofthiswonderfullycomplex,quintessentiallyhumanpieceofanatomycanbetracedbacktothefinsofancientfish.It’sanincredibleevolutionarystorythatwecannowunravel.NEILSHUBINVOWhenTiktaalikwasfirstconceived,likeeveryanimalthathaseverlived,itstartedasasinglecell,whichslowlyformedintoabody.Smallbudsappearedandgenes,likeSonicHedgehog,shapedthemintofins.Overmillionsofyears,finsliketheseevolvedintoamyriadofforms.Likethelimbofthisearlyamphibianwitheightfingers.As

millionsmoreyearspassed,newvariationsemerged.Fromtheclawedlimbsofreptilesthatwouldcolonizedryland.Tothepowerfularmsofprimatesthatcouldtraversethroughthetrees.Untileventuallyaremarkablepieceofanatomyarosethatwoulditselftransformtheworld,thehumanhand.Thishistoryisnotjustinourbone,fleshandmuscle;it’sinourDNA.Andthat’swhatconnectsusallthewaybacktoourinnerfish.Fundamentalportionsofourownbodies…NEILSHUBINOC…originallycameaboutinfishlivinginwater,andthegreattransitionfromlifeinwatertolifeonlandsetthestageforawholenewsetofanatomicalinventionsthatwerethemselvestoformthecoreforourownhumanity.MUSICOUT